Selection of appropriately sized dies in a die drafting operation has heretofore involved choosing ever smaller die apertures based on the experience or set of experiences of an operator, which are often reduced to a chart or series of approximation calculations.
Most die draft selection techniques rely on standard area reductions between each die to calculate the die draft. This method works well when the selected sizes are based on standard reductions, such as Brown and Sharp size reductions. It may not work well for odd sizes or unusual rod materials. Problems can also arise when drawing non-standard materials or special alloys.
One known method of selecting the various dies is described in "Wire Drawing Practice: Die Drafting," by Bobby C. Gentry, published in Wire Journal, August 1975. This calculation-based approximation technique is based on many years of practice and experience. Since each successive die size calculation relies on previous die size calculations, each calculation must be carefully verified to eliminate errors in the die draft schedule.
A chart or table is prepared from calculations incorporating a fixed ten percent slip rate between the capstan surface velocity ("capstan velocity") and the wire linear velocity ("wire velocity"). An optimal die draft schedule may require repeated adjustment of calculated values. A tenth-gauge reduction table is usually generated, from which the dies are selected. This time-consuming effort is imprecise and expensive, as it may, if erroneous, result in wire breaks which require restringing the rod, and is inherently consumptive of the engineer's valuable time.
As can be readily appreciated, the analysis of hundreds of wire drafting parameters in producing an efficient and effective wire drafting schedule for various rod and wire sizes on a given wire-drafting machine can be an extraordinarily time-consuming task because of the numerous combinations and permutations of the relevant parameters, and may require repeated adjustments, even if slight in magnitude, in order to provide effective and efficient operation of the wire drawing machine or machines.
In view of the foregoing limitations and shortcomings of the prior art methods and apparatus, as well as other disadvantages not specifically mentioned above, it should be apparent that there exists a need in the art to eliminate imprecision and time-consuming trial-and-error methods of die selection. It is, therefore, a primary object of this invention to fulfill that need by providing a computer-based system of selecting dies for a given rod/wire size requirement.
An advantage of the present invention resides in the fact that the intellectual expertise of the skilled engineer and operator are combined in a computer-based application wherein little skill in generating the die draft schedule is required for reliable and economic operation.